The aim of the study was to determine the effect of four different essential oils on the sensitivity of allergenic fungi i.e. Alternaria alternata, Botrytis cinerea and Cladosporium cladosporioides. The studied fungi were isolated from infected fennel. The tested oils were added to Potato Dextrose Agar medium at the concentrations of 0.1 mg/mL, 0.25 mg/mL and 0.5 mg/mL. The activity of the oils on the inhibition of the linear growth of mycelium was evaluated by measuring of fungal colonies, while the fungistatic activity was evaluated on the basis of the percentage growth inhibition of fungal colony and calculated according to Abbot’s formula. The sensitivity of the tested isolates of fungi was variable and depended on the type and concentration of the studied essential oils. The most effective antifungal effect on all tested fungi was in essential oil of oregano even at the concentration of 0.1 mg/mL, while the weakest effect was in essential oil of grapefruit at all studied concentrations. Moreover, oregano essential oil caused degradation and decay of mycelium and spores. Essential oils are potential and promising antifungal agents used as bio fungicides in plant protection and indoor air disinfection. Therefore, further in vivo studies should be carried out.